They know that between
them are 4 hats, 2 x black and 2 x white, but they do not know which colour
they are wearing.

In order to avoid being
shot one of them must call out to the executioner the colour of their hat. If
they get it wrong, everyone will be shot.

They are not allowed to
talk to each other and have 10 minutes to fathom it out.

After 1 minute:

Q Which one of them calls
out ?

Q. Why is he 100% certain
of the colour of his hat ?

This is not a trick question.

There are no outside influences
nor other ways of communicating. They cannot move and are buried in a straight
line. So A & B can only see their respective sides of the brick wall, C
can see B and D can see B & C.

(The fact that the picture
is on a slight slope is just due to me scanning it badly. The wall is *not*
reflective. The picture is not drawn badly: that *is* the way the poor men are
buried. To solve it, think buddhist. If I were to rewrite it, perhaps "after
one minute" could be changed:

For instance, it might
say: "although they have obviously made dubious career moves, these men
are not stupid";

or :" these guys had obviously
made a serious mistake in hitting on the general's daughter, but he was a fair
man, and none had been excessively traumatised prior to burial"